/*
 *  call-seq:
 *     dvector.reverse_each_with_index {|x,index| block }  ->  array
 *  
 *  Same as <code>Dvector#each_with_index</code>, but traverses _dvector_ in reverse
 *  order.
 *     
 *     a = Dvector[ 1, 0, -1 ]
 *     a.reverse_each_with_index {|x,i| print "(", x, ",", i, ") " }
 *     
 *  produces:
 *     
 *     (-1,2) (0,1) (1,0) 
 */ VALUE dvector_reverse_each_with_index(VALUE ary) {